This invention relates to an apparatus capable of measuring the profile of a line spectrum emitted from a light source, and more particularly to an apparatus of the kind above described which can measure such a profile with high resolution.
A Fabry-Perot interferometer has heretofore been used for the spectrophotometry with very high resolution. However, it has been difficult to use the Fabry-Perot interferometer for the spectrophotometry of an emission having a wavelength smaller than 300 nm, and it has been utterly impossible to use the interferometer for the spectrophotometry of an emission having a wavelength smaller than 250 nm, since the reflection efficiency of the etalon becomes extremely low at short wavelengths. The spectrophotometry with very high resolution is especially indispensable for the measurement of the profile of emission line spectrums of atoms. It is commonly known that, in most of the chemical elements, the atom's primary resonance line widely utilized for the spectroscopic analysis of the elements lies within the wavelength range of from 170 nm to 300 nm, and, in view of such short wavelengths, the Fabry-Perot interferometer is not suitable for the purpose. It is the established fact that the profile of the line spectrum emitted from a light source of atomic spectrum is the principal factor which determines the sensitivity of absorption and the linearity of calibration curves in the field of atomic absorption analysis too. In spite of the above fact, the profile of the emission line spectrum of most of the elements has still been a matter of assumption due to the difficulty or impossibility of measurement. While hollow cathode lamps are now widely used in the field of atomic absorption analysis, it is the present status that the emission spectrum profile is not measured so frequently.